The ability to transfer save files across Wii U and 3DS versions of the new Monster Hunter series failed to go live on the game's North American launch day yesterday, despite being featured in the main trailer for the game.

Gamers in North America can merrily play through the Nintendo console and portable versions of Monster Hunter 3 Ultimate, but the ability to move save files from one machine to the next is dependent on a free, downloadable 3DS app that has yet to appear on the system's online store. Until it does, the Wii U version's save-transfer menu option is but a tease.

"The Monster Hunter 3 Ultimate Packet Relay Tools and the Monster Hunter 3 Ultimate Data Transfer Program are not yet live on the Nintendo eShop," a Capcom rep confirmed to Kotaku over e-mail late last night. "Capcom is working closely with Nintendo to make these available for download as soon as possible and apologize for the delay."

Monster Hunter is one of the most popular game series in Japan, a phenomenon of Call of Duty or Pokémon proportions. It kept Sony's PSP popular in that country even as the system fell into the shadows elsewhere.

The Monster Hunter games are fantasy-themed adventures that let up to four players arm heroes with outlandish swords, bows and other weapons as they hunt a menagerie of otherworldly beasts.

The new Wii U and 3DS games, which are sold separately, update the 2009/2010 Wii release of Monster Hunter Tri with up-razzed graphics and added content. While players can solo through the game, they can play online with others on Wii U or with fellow 3DS owners locally.

Once the app goes live players will be able to move their progress across machines so they can play on their TV or away from it. We'll update this post when it is available.

UPDATE 3/20 9:48PM ET: A Capcom rep now says: "As you know, the Monster Hunter 3 Ultimate Packet Relay Tools and the Monster Hunter 3 Ultimate Data Transfer Program are not yet live on the Nintendo eShop. Nintendo is working very closely with us to get these live as soon as possible and we anticipate that they will both be available on the Nintendo eShop by Friday, March 22. We sincerely apologize for the delay and appreciate that eager fans are looking forward to the feature set offered by the two apps."